Err 99 is Canon's catch-all designation for Unknown Problem. It could be anything -- a lens problem, a battery problem, an electronic problem...
Often, this error goes away if you take out the batteries (including the little watch battery in the battery case), wait a few minutes, then put the batteries back in. If it's a lens problem, though, you might take the lens off as well as take the batteries out (you can put the cap on the lens mount to prevent dust). Then try to turn the camera on without the lens mounted. If you still get the error, definitely return the kit. If not, you may have a lens problem. You could still exchange the kit, but at least you know what you're dealing with.